Laser based materials processing has been used in a variety of applications such as drilling, cutting, scribing, and trimming. In some applications, the ability for a processing beam to be split into several processing beams is particularly advantageous. For example, U.S. Pat. No. 8,178,818 to Baird et al. discloses a laser processing system that splits a pulsed laser beam into multiple beamlets that are delivered to a target. U.S. Pat. No. 7,666,759 to Couch et al. discloses another multi-beam processing system. For some laser material processing applications such as micromachining, the position of laser beam waists must be controlled to within less than 1 μm over long periods of time. This low drift requirement is tighter than that available with conventional beam deflectors or scanners, and improved methods and apparatus are needed.